MathDB
Problems
Contests
National and Regional Contests
Iran Contests
Iran Team Selection Test
2017 Iran Team Selection Test
1
Number Theory from Iran TST 2017
Number Theory from Iran TST 2017
Source: 2017 Iran TST third exam day1 p1
April 26, 2017
number theory
Iran
Iranian TST
Problem Statement
Let
n
>
1
n>1
n
>
1
be an integer. Prove that there exists an integer
n
−
1
≥
m
≥
⌊
n
2
⌋
n-1 \ge m \ge \left \lfloor \frac{n}{2} \right \rfloor
n
−
1
≥
m
≥
⌊
2
n
⌋
such that the following equation has integer solutions with
a
m
>
0
:
a_m>0:
a
m
>
0
:
a
m
m
+
1
+
a
m
+
1
m
+
2
+
⋯
+
a
n
−
1
n
=
1
lcm
(
1
,
2
,
⋯
,
n
)
\frac{a_{m}}{m+1}+\frac{a_{m+1}}{m+2}+ \cdots + \frac{a_{n-1}}{n}=\frac{1}{\textrm{lcm}\left ( 1,2, \cdots , n \right )}
m
+
1
a
m
+
m
+
2
a
m
+
1
+
⋯
+
n
a
n
−
1
=
lcm
(
1
,
2
,
⋯
,
n
)
1
Proposed by Navid Safaei
Back to Problems
View on AoPS